Just to make absolutly sure: You want to draw onto a game, you did
not write yourself, and you
don't have the sourcecode or a kind of interface for. True?
In that case the code you link to shows how you may create HUD-like graphics, but these are still very far away from being displayed in a third party game. For this, you'll have to either hook some functions the DX DLLs, or replace them etirely with your own versions that hang in between the game and the original DLLs. Both methods seem to be quite difficult, and I wasn't able to find much detailed postings or techtalk dealing with this. To be more precise: None that told more than "it's got to be possible, others like Fraps do it"
PS: Questions for complete source translations are best served with a reasonable offer regarding payment
"When one person suffers from a delusion, it is called insanity. When a million people suffer from a delusion, it is called religion." (Richard Dawkins)